Coring operations were conducted in the west basin of Clear Lake during July and August 1980 to produce a regional Quaternary reference section. A 177-m-long core (CL-80-1) was taken, which also augments and extends a previous study of eight shorter cores collected from Clear Lake in 1973. Core CL-80-1 was continuously cored in 7.5 m of water, and 66.5 percent recovery was achieved. The sediments are composed primarily of clayey and silty sapropelic mud similar to those presently being deposited in the lake, and are interbedded with local coarse sand and gravel deposits and thin volcanic ash beds. Coring was terminated when coarse rounded gravel and cobbles of Franciscan assemblage lithology were encountered. The location of core CL-80-1 is between two other core sites of the 1973 series of cores, one of which (CL-73-4) is 115 m long and contains a well-defined, uninterrupted pollen and physical stratigraphic record from the present to about 130,000 years ago. Paleomagnetic and preliminary pollen analyses of core CL-80-1 are complete and comparison of these results with those of core CL-73-4 suggest that the new core represents a record from the present to about 175,000 years ago.
